Android introduces a sophisticated permission-based security model, whereby an application declares a list of permissions, which are approved by the user at application installation. These permissions guard specific functionalities on the device, including some security and privacy-sensitive APIs such as access contacts, e.g., an address book.
Modern operating systems such as mobile, iOS, and Windows 8 have brought about the advent of big, centralized application stores that host third-party applications for users to view and install. Google Play, the official application store for mobile, hosts both free and paid applications together with a variety of metadata including the title and description, reviews, ratings, and so on. Additionally, it also provides the user with the ability to study the permissions requested by an application.